The filing doesn't include sketches of the product or details (Microsoft specifically requested confidentiality for that stuff) , but one test report does reveal that it will come in three sizes: small, medium, and large.

There's also a Bluetooth Low Energy radio in all three versions, as Windows Central pointed out, which is commonly found in many wrist-worn devices.

Last week Forbes reported that Microsoft's upcoming wearable will focus on fitness and is likely to work with iOS and Android devices. This lines up with previous reports too, such as one from Tom's Hardware back in June.

The website reported that Microsoft is working on a slim fitness band that will include a display on the inside of the wrist.